Improving soil engineering properties is an inevitable process before construction on soft soil. Increasing soil strength with chemical stabilizing agents, such as cement, raises environmental concerns. Therefore, sustainable solutions are in high demand. One of the promising solutions is the usage of biopolymers. Five biopolymer types were investigated in this study: Xanthan Gum, Beta 1,3/1,6 Glucan, Guar Gum, Chitosan, and Alginate. Their effect on the soil strength improvement was experimentally investigated by performing unconfined compression, splitting tensile, triaxial, and direct shear tests. All tests were performed with different biopolymer concentrations and curing periods. Additionally, in order to have an insight on the susceptibility to natural elements, plain soil, and biopolymer-treated specimens were exposed to real atmospheric conditions. The extensive experimental results showed that the soil strength tends to increase with the increase of biopolymer concentration and with the curing time. However, it was shown that the soil strength does not considerably change after a certain biopolymer concentration level and curing time. Furthermore, it has been observed that the biopolymer-treated specimens showed better resistance to the influence of the environmental conditions. In general, Xanthan Gum, Guar Gum, and Beta 1,3/1,6 Glucan showed the most dominant effect and potential for the future of sustainable engineering.